The author of the 5:2 diet explains why eating healthy is more important than exercise

Michael Mosley, author of the 5:2 diet and the "Clever Guts Diet," spoke to Business Insider UK and explained why a healthy diet is much more important than exercise when it comes to losing weight.

Mosley said, "An awful lot of people go to the gym in January in order to lose weight. They think if they go to the gym and cycle a bit and do a bit of running then they will obviously shed some of those kilos. The reality is that that does not happen which is why the vast majority of people give up."

"In order to lose a kilo of fat you would probably have to run two marathons. So in many ways it is obviously much easier simply to reduce the amount of calories you eat rather than trying to run them off because you have to do so much exercise to burn calories."

"What I would recommend is yes, you do exercise because that's going to improve your mood and it's very helpful once you've lost weight but hoping that simply by doing exercise you're going to lose weight is really over optimistic."

"You should be aware of these tendencies but as I said if you really want to lose weight the only way to do that is by reducing the calories you eat and switching the sort of food you eat."